1. Field of the Disclosure
This disclosure relates in part to adsorption-desorption materials, in particular, to crosslinked polyvinyl-amine materials, and linear polyvinyl-amine materials, and to processes for the preparation of these materials. This disclosure also relates in part to the use of these materials in the selective removal of CO2 and/or other acid gases from a gaseous stream containing one or more of these gases.
2. Discussion of the Background Art
The selective removal of carbon dioxide from mixed gas streams is of great commercial value. Commercially, carbon dioxide may be used for reinjection into gas or liquid hydrocarbon deposits to maintain reservoir pressure and for enhanced product recovery. Due to the advanced age of many producing reservoirs worldwide and the ever-increasing challenge of meeting demand, the expanding use of enhanced oil recovery (EOR) methods is becoming more widespread.
Typically the source of carbon dioxide for EOR is the producing hydrocarbon stream itself, which may contain anywhere from less than 5% to more than 80% of CO2.
Additionally, it is desired to capture CO2 from flue gas of various combustion sources, where the stream contains less than about 15% of CO2 and its temperature is relatively high. Yet another need for CO2 capture technology is for the pre-combustion capture of CO2 from shifted syngas produced in fuel gasification processes.
Conventional methods for CO2 capture include cryogenic distillation/condensation, absorption using liquid solvents, such as amine scrubbing, or sorption using solid sorbents, such as pressure swing adsorption (PSA) and/or temperature swing adsorption (TSA). However, with present technologies, all of these processes require a large temperature decrease of the gas stream to enable CO2 condensation or sorption. Conventional methods (PSA, TSA, amine scrubbing) require CO2 uptake at relatively low temperatures (e.g., less than 50° C.). Sorbent/solvent regeneration (CO2 desorption) is accomplished by a step change decrease in CO2 partial pressure (PSA), and/or by a temperature increase to above about 100° C. (TSA, amine scrubbing). In all of these cases, CO2 capture costs depend significantly on the required heat exchange capacities and energy requirements for gas cooling/heating, the costs for steam generation for CO2 desorption, and the high equipment and energy costs associated with CO2 recompression.
Conventional amine scrubbing is based on the chemistry of CO2 with amines to generate carbonate/bicarbonate and carbamate salts. Commercially, amine scrubbing typically involves contacting the CO2 and/or H2S containing gas stream with an aqueous solution of one or more simple amines (e.g., monoethanolamine). The process requires high rates of gas-liquid exchange and the transfer of large liquid inventories between the absorption and regeneration steps and high energy requirements for the regeneration of amine solutions. This process is challenged by the corrosive nature of the amine solutions. These challenges limit the economic viability for large-scale applications (e.g., large combustion sources and power plants) utilizing conventional technologies.
The growing need to incorporate carbon capture and sequestration (CCS) into fossil fuel-based power generation, has triggered accelerating research into alternatives to conventional amine scrubbing technology. Cyclic adsorption technologies (e.g., PSA and TSA) using solid adsorbents are also well-known in the gas purification industry. These processes avoid many of the limitations of amine scrubbing described above, but suffer from a lack of adsorbents having sufficiently selective CO2 adsorption under the humid conditions always present in combustion flue gas, as well as the commercial viability of large scale operation.
Due to the ever increasing use of CO2 re-injection for enhanced oil recovery, technology that reduces the cost of CO2 capture directly reduces hydrocarbon production costs. In addition, if anticipated future restrictions on CO2 emissions are mandated, a low cost method for CO2 capture will be a critical need as a part of CCS.
Carbon dioxide is a ubiquitous and inescapable by-product of the combustion of hydrocarbons. In addition to the use of CO2 for EOR, there is growing concern over its accumulation in the atmosphere and its role in global climate change. Therefore in addition to the commercial benefits of CO2 recovery, environmental factors may soon require its capture and sequestration. For these reasons the separation of CO2 from mixed gas streams is a rapidly growing area of research.
Therefore, a need exists for developing commercially viable alternative methods and adsorbent materials for the selective removal of CO2 from gas mixtures, particularly adsorption technologies and adsorbent materials having economic viability for large-scale (e.g., large combustion sources and power plants) applications.